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KaMiKaZi_t0M
September 9th, 2017, 10:36 AM
Hello all.
I've been interested in computers all my life, and intrigued by vintage PC's however today I bought my first at a tagsale! It's a Compaq Portable, seemed to have been nicely cared for. I plugged it in, threw the power switch and heard a very loud pop and smelled the bad smell. My fiance said the monitor lit up momentarily before the pop. Currently the fan spins however nothing more. I removed the plastic panels and I see no popped capacitors or anything out of the ordinary. Are there any common failures like this or a troubleshooting guide I should follow?
Thank you,
Tom

Stone
September 9th, 2017, 10:57 AM
I think your initial instinct was correct. Check the caps more thoroughly. It sounds like there is a shorted cap in there.

flashedbios2012
September 9th, 2017, 11:37 AM
Its most definitely a popped capacitor. I'd bet the farm on it!

KaMiKaZi_t0M
September 9th, 2017, 12:34 PM
Thank you for the help folks. If the fan is spinning, that would rule out a failed cap on the PSU, right? I'm looking pretty thoroughly, the sound and smell made it seem like the failure should have been obvious, however not to a novice obviously!
Tom

modem7
September 9th, 2017, 01:50 PM
My fiance said the monitor lit up momentarily before the pop.
Sometimes, when failing tantalum capacitors produce a shower of sparks, all that is seen on the capacitor is a small hole.
See far left photo at [here (http://minuszerodegrees.net/failure.htm)].

T-R-A
September 9th, 2017, 09:30 PM
If the fan is spinning, that would rule out a failed cap on the PSU, right?

Nope.

Power supplies are notoriously bad on the old Compaq Portables. I've lost 2 of them (Portable II's) due to fried capacitors in the P/S. And one of them was pretty nicely upgraded to 1MB Ram, IDE HDD and 1.44MB FDD.

alank2
September 10th, 2017, 02:08 PM
I went through the same thing. The pop/fizzle could be the filter in the box you plug the AC cable into - but I think it fails quickly and you can keep using it. The big problem you have is likely a shorted tantalum capacitor. I replaced a couple of them on mine. The power supply board will detect the short and shut down. Unplug the power supply from the headers and measure the rails to ground to see if any are shorted. If they are, then find the shorted caps and remove them!